Apparatus and method for raising the pile of a sheet of cloth web

ABSTRACT

An apparatus for raising the pile of a sheet of cloth web comprising
         a transport means for transporting the sheet of cloth web along a path; and,   at least one primary air knife disposed at a distance from a first side of said path and arranged such that it extends across the path and is inclined such that the air stream from the air knife is incident to the path at an angle to the normal to the path.

The present invention relates to an apparatus and method for raising the pile of a sheet of cloth web. More particularly, but not exclusively the present invention relates to an apparatus comprising an air knife arranged such that the air stream from the knife is incident on the cloth web at an angle to the cloth web.

After a towel has been manufactured from a cloth web it is desirable to raise the pile of the towel. This gives the appearance of a thicker material and also feels softer. This has aesthetic appeal for a consumer. Currently it is the normal practice after manufacture to dry a towel in a fan assisted over. This has a limited effect on raising the pile of the cloth web.

The present invention seeks to overcome this problem.

The present invention provides an apparatus for raising the pile of a sheet of cloth web comprising a transport means for transporting the sheet of cloth web along a path; and, at least one primary air knife disposed at a distance from a first side of said path and arranged such that it extends across the path and is inclined such that the air stream from the air knife is incident to the path at an angle to the normal to the path.

The apparatus according to the invention raises the pile during drying more effectively than a conventional drying oven.

Preferably, the apparatus further comprises at least one secondary air knife disposed at a distance from the opposite side of said path and arranged such that it extends across the path and is inclined such that the air stream from the secondary air knife is incident to the path at an angle to the normal to the path.

Preferably, the air stream from at least one air knife is incident at an angle of between 30 and 70 degrees to the normal to the path, preferably between 40 degrees and 60 degrees to the normal to the path, preferably between 45 degrees and 55 degrees to the normal to the path.

Preferably, the distance from the path to the at least one air knife is between 10 mm and 20 mm.

Preferably, the apparatus further comprises a plurality of primary air knives disposed on the first side of said path.

Preferably, the apparatus further comprises a plurality of secondary air knives disposed on the opposite side of said path from said primary air knives.

Preferably, the air knives are arranged such that the air stream from one air knife does not interfere with the air stream of an adjacent knife on the same side of said path.

Alternatively, the air knives are arranged such that the air stream from one air knife interferes with the air stream of an adjacent air knife on the same side of said path to produce a combined air flow which raises the pile by a greater degree than the air from the air knives in isolation.

Preferably, the distance between any air knives on the same side of the path is greater than or equal to 400 mm, preferably between 400 and 600 mm.

Preferably, the apparatus further comprises a supporting bed arranged adjacent to the path and extending at least partially along the length of the path for supporting the cloth web.

Preferably, the apparatus comprises a plurality of supporting beds preferably arranged on opposite sides of the path.

Preferably, at least one supporting bed is arranged on the opposite side of the path to an air knife.

Preferably, the apparatus further comprises a drive mechanism to draw the sheet of cloth web along the path; and, a tensioner at the opposite end of the path to the drive mechanism for providing the sheet of cloth web to the drive mechanism under tension.

Preferably, the at least one air knife is fed air via a manifold system.

Preferably, the air knives and at least a portion of the path are arranged within a substantially air tight housing, the housing comprising an air output, the output comprising a filter.

In a further aspect of the invention there is provided a method of raising the pile of a sheet of cloth web comprising the steps of

-   -   (a) providing an apparatus for raising the pile of a sheet of         cloth web, the apparatus comprising a transport means for         transporting the sheet of cloth web along a path and at least         one primary air knife disposed at a distance from a first side         of said path and arranged such that it extends across the path         and is inclined such that the air stream from the air knife is         incident to the path at an angle to the normal to the path;     -   (b) providing the cloth web to the transport means to be         transported along the path; and,     -   (c) providing air to the air knives to raise the pile of the         cloth web.

Preferably, the sheet of cloth web is drawn past at least one air knife at a speed of between 5 and 25 metres per minute.

Preferably, the moisture content of the cloth web at the start of the path comprises between 70% and 80% of the total weight of the cloth web.

The present invention will now be described by way of example only and not in any limitative sense with reference to the accompanying drawing.

FIG. 1 shows a cross section of an apparatus according to the invention.

Shown in FIG. 1 is an apparatus 1 according to the invention comprising a pair of primary air knives 2, 3 above a path 4 and a pair of secondary knives 5, 6 below the path 4. The knives 2, 3, 5, 6 are held at a distance away from the path 4 and are arranged such that the air stream emitted from the air knives 2, 3, 5, 6 is incident on the path 4 at an angle to the normal to the path 4.

Air knives are known in the art. Each air knife 2, 3, 5, 6 of this embodiment is an elongate chamber 7 with a narrow section of the chamber wall, running parallel to the longitudinal axis of the chamber, removed to form an outlet 8. To improve the quality of the air stream, a nozzle 9 extends from the outlet 8 of each air knife 2, 3, 5, 6. Air is fed from a manifold 10 into each air knife 2, 3, 5, 6 via inlets (not shown) in the chamber wall arranged at intervals along the opposite side of the chamber wall to the outlet 8. When air is pumped into an air knife 2, 3, 5, 6 it escapes via the outlet 8 forming a blade of high pressure air in the form of an air stream. The manifold 10 of this embodiment is comprised of a master manifold (not shown) and a plurality of sub manifolds 10. The sub-manifolds 10 are connected to the air knife inlets. Having numerous inlets produces a greater degree of homogeneity in the air pressure within the air knife chamber so as to give a more uniform air pressure and velocity in the air stream leaving the nozzle 9. In this embodiment each master manifold us used to feed two air knives 2, 3, 5, 6.

The distance between the tip of the air knife nozzle 9 and the path 4 in this embodiment is between 10 and 20 mm. In another embodiment it is between 5 and 30 mm.

In this embodiment the air stream from each of the air knives 2, 3, 5, 6 is directed at an angle of 50 degrees to the normal to the path 4. In another embodiment the air stream is directed at an angle preferably between 40 and 60 degrees and more preferably between 30 and 70 degrees. The air knives can be adjustable to adjust the angle between air knives and the path.

To the right of FIG. 1 there is an input 11 for a cloth web 12. To prepare the apparatus for use, one end of a sheet cloth web 12 is fed through a tensioning device 13, passed along the path 4 and fed through the outlet 14. External to the machine of this embodiment and not shown in FIG. 1 is a driving mechanism. The driving mechanism acts to draw the cloth web 12 through the machine when in operation. In one embodiment it would be possible to do this by way of a revolving drum on to which the end of the cloth web 12 is attached. The tensioning device 13 is comprised of four rollers 15-18 held in an orthogonal arrangement to the path 4, each of which is free to rotate about its longitudinal axis. On roller 17 of the four rollers 15-18 is a tensioning roller and is attached to a weight via a pivoted connecting arm (not shown). The tensioning roller 17 sits in a loop of cloth web 12. As the driving mechanism draws the cloth web 12 through the machine the tensioning roller 17 pulls vertically downward on the loop of cloth web 12 thereby tensioning the web 12. The pivoted weight can be altered to adjust the tension of the cloth web 12. The combination of rollers also acts to straighten and align the cloth web 12. The speed of the cloth web 12 will be a design feature dependant on the desired appearance of the cloth web 12 and various physical parameters, such as, for example, the angle of the air streams incident to the normal of the path 4. In this embodiment the speed of the cloth web 12 is preferably between 5 and 25 metres per minute.

The air streams emitted from the outputs 8 of the air knives 2, 3, 5, 6 are high pressure jets of air along the length of the air knives 2, 3, 5, 6. The pressure and velocity of the knives will be dependent on the air pumped into the knives and the output nozzle. In this embodiment the knives 2, 3, 5, 6 are 3.2 m in length with a nozzle width of approximately 1 mm. Each knife 2, 3, 5, 6 preferably outputs a volume of between 1600 to 1800 cubic metres per hour. In order to prevent the cloth web 12 being deflected by the pressure, support beds 19, 20 are provide to keep the distance between the cloth web 12 and air knife 2, 3, 5, 6 substantially constant. The beds 19, 20 will traverse the width of the cloth web 12 sheet such that it is sufficiently supported. In this embodiment, the beds 19, 20 are made from polished stainless steel and are 700 mm wide. In another embodiment it may be desirable to have them made from another suitable material and the same or a different width.

The turbulence created by the air stream of a first air knife 2, 5 is likely to disturb and interfere with the air stream produced by a second air knife 3, 6 if the two air knives are placed too close together. This will affect the performance of the air stream and its ability to raise the pile in the cloth web 12. In order to reduce this effect the air knives 2, 3, 5, 6 should be placed at a suitable distance apart. This will be a design feature dependant on the velocity and pressure of the air stream. In this embodiment, the distance between the two air knives 2, 3, 5, 6 disposed on the same side of the path 4 are 500 mm apart. Preferably the distance is greater than 400 mm and between 400 and 600 mm. It is also desirable to provide a suitable separation between primary air knives 3, 6 and secondary air knives 2, 5. In this embodiment the air knives 2, 3, 5, 6 are arranged such that the web 12 drawn along the path 4 passes the two primary air knives 3, 6 before passing the two secondary air knives 2, 5. The distance between the second primary air knife 6 and the first secondary air knife 2 is 300 mm. In another embodiment the air knives 2, 3, 5, 6 may be distributed along the path 4 in a different order, for example, primary-secondary-primary-secondary. In this embodiment there is a housing (not shown) that surrounds the apparatus. It is desirable to have suitable spacing from the front wall of the housing and the first air knife 3 to prevent unnecessary air leakage where the cloth web enters the housing. This also applies to the rear of the air knife 5 closest to the output 14 of the apparatus 1. The spacing in this embodiment from the front wall to the first air knife 3 is 250 mm, and from the last air knife 5 to the rear wall, 550 mm.

In an alternative embodiment adjacent air knives are positioned sufficiently close together for the air streams of the air knives to interact to produce a combined air flow on the surface of the web. The combined air flow may be more efficient at raising the pile of the web than the air flow of the individual air knives alone.

In this embodiment the direction of air flow from the air knives is against the direction of travel of the cloth web as shown. In an alternative embodiment the direction of air flow can be in the direction of travel of the cloth web.

In order to get the maximum amount of rise in the pile of the cloth web 12 it is desirable for the cloth web 12 to be wet. In this embodiment it is preferred for the moisture content of the web 12 upon approaching the first air knife 3 should be between 70% and 80% expression. That is, the cloth web moisture content should be between 70% and 80% of the dry weight of the cloth.

In this embodiment, the cloth web 12 is made from a cotton loop pile towelling fabric. When blown with the air streams the cloth web 12 gives up loose strands and particles of cotton which collect to make cotton fly. To allow the air emitted from the air knives 2, 3, 5, 6 to escape, the housing incorporates a filtered output (not shown). This can be local to the housing or situated at a remote location with the air being ducted away from the housing.

Through the embodiment disclosed herein above describes a cotton pile towel fabric with a specific arrangement of air knives 2, 3, 5, 6, the man skilled in the art will realise that different configurations and different materials may be used. Form example, a different king of suitable material might be velour or any pile type fabric. 

1. An apparatus for raising the pile of a sheet of cloth web comprising: a transport means for transporting the sheet of cloth web along a path; and, at least one primary air knife disposed at a distance from a first side of said path and arranged such that the air knife extends across the path and is inclined such that the air stream from the air knife is incident to the path at an angle to the normal to the path.
 2. An apparatus as claimed in claim 1, further comprising at least one secondary air knife disposed at a distance from an opposite side of said path and arranged such that the secondary air knife extends across the path and is inclined such that the air stream from the secondary air knife is incident to the path at an angle to the normal to the path.
 3. An apparatus as claimed in claim 1, wherein the air stream from the at least one air knife is incident at an angle of between 30 and 70 degrees to the normal to the path.
 4. An apparatus as claimed in claim 1, wherein the distance from the path to the at least one air knife is between 10 mm and 20 mm.
 5. An apparatus as claimed in claim 1, further comprising a plurality of primary air knives disposed on the first side of said path.
 6. An apparatus as claimed in claim 5, comprising a plurality of secondary air knives disposed on an opposite side of said path from said primary air knives.
 7. An apparatus as claimed in claim 5, wherein the air knives are arranged such that the air stream from one air knife does not interfere with the air stream of an adjacent knife on the same side of said path.
 8. An apparatus as claimed in claim 5, wherein the air knives are arranged such that the air stream from one air knife interferes with the air stream of an adjacent air knife on the same side of said path to produce a combined air flow which raises the pile by a greater degree than the air from the air knives in isolation.
 9. An apparatus as claimed in claim 5, wherein the distance between any two air knives on the same side of the path is greater than or equal to 400 mm.
 10. An apparatus as claimed in claim 1, further comprising a supporting bed arranged adjacent to the path and extending at least partly along a length of the path for supporting the cloth web.
 11. An apparatus as claimed in claim 10, comprises a plurality of supporting beds, preferably arranged on opposite sides of the path.
 12. An apparatus as claimed in claim 11, wherein at least one supporting bed is arranged on the opposite side of the path to an air knife.
 13. An apparatus as claimed in claim 1, comprising a drive mechanism to draw the sheet of cloth web along the path; and, a tensioner at an opposite end of the path to the drive mechanism for providing the sheet of cloth to the drive mechanism under tension.
 14. An apparatus as claimed in claim 1, wherein the at least one air knife is fed air by a manifold system.
 15. An apparatus as claimed in claim 1, wherein the air knives and at least a portion of the path are arranged within a substantially air tight housing, the housing comprising an air output, the air output comprising a filter.
 16. A method of raising the pile of a sheet of cloth web comprising the steps of: providing a transport means; providing the web to the transport means; transporting the cloth web on the transport means along a path; providing at least one primary air knife disposed at a distance from a first side of the path and arranged such that the air knife extends across the path and is inclined relative to the path; and, providing air to the air knives at an angle to the normal to the path to raise the pile of the cloth web.
 17. A method as claimed in claim 16, whereby the sheet of cloth web is drawn past at least one air knife at a speed of between 5 and 25 metres per minute.
 18. A method as claimed in claim 16, wherein the moisture content of the cloth web at the start of the path comprises between 70% and 80% of the total weight of the cloth web.
 19. An apparatus as claimed in claim 1, wherein the air stream from the at least one air knife is incident at an angle of between 40 degrees and 60 degrees to the normal to the path.
 20. An apparatus as claimed in claim 1, wherein the air stream from the at least one air knife is incident at an angle of between 45 degrees and 55 degrees to the normal to the path.
 21. An apparatus as claimed in claim 5, wherein the distance between any two air knives on the same side of the path is between 400 and 600 mm. 